Maximum Substrate Research Articles

Inhibition Kinetics of Polyphenol Oxidase from Purple Sweet Potato by Ascorbic Acid

With catechol as a substrate, some kinetic parameters, including Michaelis constant (Km), maximum reaction velocity (Vmax) and substrate inhibition constant (KI) for the reaction catalyzed by polyphenol oxidase (PPO) from purple sweet potato (PSP) were mainly studied here by spectrophotometry. Kmand Vmaxwere determined depending on bi-reciprocal diagram of Lineweaver-Burk and Hanes-Woolf diagram respectively, with Kmof 12.06 mM and Vmaxof 43.66 mM·min. The effects of four various inhibitors on PPO activity were different. Ascorbic acid (AA) and phytic acid (PA) showed strong inhibitory effects, with AA of the highest effect and citric acid (CA) the lowest. Among these inhibitors, AA was a reversible competitive inhibitor with KIof 15.26 mM, which was significant and instructive to the quality and benefit improvement of processed PSP products.

Biokinetic Studies in the Treatment of Tannery Effluent

The present investigation deals with the anaerobic treatment of composite tan liquor with varying organic loads. BOD of the influent and effluent and MLSS of reactor were determined at various detention times to generate data for kinetic coefficients. The kinetic coefficients k (maximum substrate utilization rate), Ks (half velocity constant), Y (cell yield coefficient) and Kd (decay coefficient) were found to be 1.66 day-1, 1132 mg/L, 0.05 and 0.22 day-1, respectively. Overall BOD removal rate constant ‘K’ was found to be 1.46 day-1. The studies showed that an optimum BOD influent load of 0.8 Kg BOD/m3/day with 3 days retention time could be adopted to yield about 97 percent BOD reduc¬tion. The Bio-kinetic coefficients were evaluated using modified Monod’s equations to study the metabolic performance of the digestion process.

Treatment of wastewater containing high concentrations of terephthalic acid by Comamonas sp. and Rhodococcus sp.: kinetic and stoichiometric characterization

AbstractIn this work, terephthalic acid degradation was studied with two strains that were isolated and identified as closely related to Comamonas (99%) and Rhodococcus (99%) genus. A characterization of both strains was carried out during batch experiments performed at two oxygen transfer capacities (0.094 ± 0.011 and 0.538 ± 0.042 g O2/L/h) and five concentrations of terephthalic acid (2.5 to 15.0 g/L). Maximum degradation rates of 0.073 ± 0.004 and 0.062 ± 0.003 g TOC/L/h, were observed, for Comamonas sp. and Rhodococcus sp., respectively. However, a degradation rate of 0.159 ± 0.011 g TOC/L/h was reached with a mixed culture. Haldane, Aiba, Edwards and Andrews models were used to fit terephthalic acid degradation kinetics, being Haldane the model that best fitted the results. Several parameters were determined including, maximum growth rate, growth yield, substrate affinity and inhibition constant.

Membrane phospholipid bilayer as a determinant of monoacylglycerol lipase kinetic profile and conformational repertoire

The membrane-associated serine hydrolase, monoacylglycerol lipase (MGL), is a well-recognized therapeutic target that regulates endocannabinoid signaling. Crystallographic studies, while providing structural information about static MGL states, offer no direct experimental insight into the impact of MGL's membrane association upon its structure-function landscape. We report application of phospholipid bilayer nanodiscs as biomembrane models with which to evaluate the effect of a membrane system on the catalytic properties and conformational dynamics of human MGL (hMGL). Anionic and charge-neutral phospholipid bilayer nanodiscs enhanced hMGL's kinetic properties [apparent maximum velocity (Vmax) and substrate affinity (Km)]. Hydrogen exchange mass spectrometry (HX MS) was used as a conformational analysis method to profile experimentally the extent of hMGL-nanodisc interaction and its impact upon hMGL structure. We provide evidence that significant regions of hMGL lid-domain helix α4 and neighboring helix α6 interact with the nanodisc phospholipid bilayer, anchoring hMGL in a more open conformation to facilitate ligand access to the enzyme's substrate-binding channel. Covalent modification of membrane-associated hMGL by the irreversible carbamate inhibitor, AM6580, shielded the active site region, but did not increase solvent exposure of the lid domain, suggesting that the inactive, carbamylated enzyme remains intact and membrane associated. Molecular dynamics simulations generated conformational models congruent with the open, membrane-associated topology of active and inhibited, covalently-modified hMGL. Our data indicate that hMGL interaction with a phospholipid membrane bilayer induces regional changes in the enzyme's conformation that favor its recruiting lipophilic substrate/inhibitor from membrane stores to the active site via the lid, resulting in enhanced hMGL catalytic activity and substrate affinity.

Kinetic analysis on gaseous and aqueous product formation by mixed anaerobic hydrogen-producing cultures

Anaerobic hydrogen production by mixed cultures is a complex process, and information about its kinetic analysis is sparse. In this study, an integrated approach with the weighted nonlinear least-squares analysis and accelerating genetic algorithm is proposed to evaluate the kinetic parameters of biohydrogen production from a sucrose by mixed anaerobic cultures. The weighted nonlinear least-squares analysis is used to calculate the differences in gaseous and aqueous product concentrations between the predicted and the measured results, while the accelerating genetic algorithm is utilized to optimize the objective function by minimizing the total sum of the squared weighted errors. The kinetic parameters for specific maximum substrate uptake rate, substrate uptake affinity constant, yield coefficient are calculated with this approach, and are validated by the results of the independent experimental results reported in literature. This integrated approach is effective and rapid to estimate the anaerobic hydrogen production kinetics by mixed cultures.

Isolation and identification of Paracoccus sp. FD3 and evaluation of its formaldehyde degradation kinetics

A formaldehyde-degrading bacterium strain, FD3, was isolated from contaminated soil and identified as Paracoccus sp. based on partial 16S rRNA gene sequence analysis. In batch culture, the bacterium metabolized 5,000 and 8,000 mg/L formaldehyde completely within 16 and 18 h, respectively, at 30°C (pH 7.0) with agitation at 150 rpm. The degradation kinetics was found to follow a first-order model at all initial formaldehyde concentrations with regression values greater than 0.99. Formaldehyde degradation rates increased from 532.37 to 2283.04 mg/L/h as the initial concentration of formaldehyde was increased from 1,000 to 8,000 mg/L. The growth of strain FD3 on formaldehyde as a sole carbon and energy source was well described by the Luong model with a maximal specific growth rate of 0.1754/h, a half-saturation constant of 309.02 mg/L, and a maximum substrate concentration of 3875.53 mg/L. Due to its high tolerance and degradation capacity to formaldehyde, Paracoccus sp., FD3 is considered an excellent candidate for use in degrading formaldehyde in wastewaters.

Enhanced Biohydrogen Production From Wastewater And The Influence Of Operating Parameters

Enhancement of fermentative biohydrogen production was investigated both by treatment of microbial community and optimization of key parameters using the statistical methodology. The effect of temperature, initial pH, and feed to microorganisms (F/M) ratios, individually and interactively, on fermentative hydrogen production by mixed cultures was investigated in batch tests and the optimization of fermentative hydrogen production process was conducted by response surface methodology using a Box–Behnken design. The maximum hydrogen yield of 372.90 mL/g glucose was estimated at the temperature of 30.91°C, the initial pH of 8, and the F/M ratio of 0.25. The maximum hydrogen production rate of 6.55 mL/h was estimated at the temperature of 30.03°C, the initial pH of 7.27, and the F/M ratio of 1.79. The maximum substrate consumption efficiency of 98.8% was estimated at the temperature of 30.35 °C, the initial pH of 7.5, and the F/M ratio of 0.25. Total of volatile fatty acids (VFAs) and ethanol were analyzed at the end of all experiments and their changes with operational parameters were investigated. Modified Gompertz equation could describe the progress of cumulative hydrogen production in the batch tests of this study successfully.

Multiple process integrations for broad perspective analysis of fermentative H2 production from wastewater treatment: Technical and environmental considerations

The functional certainty associated with secondary or tertiary process integration towards enhancing the viability of fermentative biohydrogen (H2) production from wastewater stabilization was investigated with eleven diverse combinations of dark-fermentation (acidogenic, HA), photo-fermentation (HP for H2) and methanogenic (for CH4) processes. Based on the specificity of individual process, the biocatalyst and the feeding pH were selected and operated at uniform hydraulic retention time (48h). Individually, HP operation showed higher H2 production (4.10mmol H2) and yield (16.02mol H2/kg CODR) than of HA (3.38mmol H2, 11.33mol H2/kg CODR) which was found contrary to the observed substrate degradation. Two-stage process integration showed marked improvement in both H2 production and substrate degradation. Integration of HP with HA showed maximum H2 production while HA with HP evidenced maximum H2 yield. Integration of methanogenic process with HP documented both higher biogas production and yield. Maximum substrate degradation was evidenced with three stage sequential integration of dark-fermentation, methanogenic and photo-fermentation processes. Three-stage integration contributed for higher substrate degradation rather than energy generation, especially with HP as the terminal process. Organic flux, energy efficiency and carbon footprint analyses were used to comprehensively delineate the practical consideration of the integrated processes.

Numerical modeling of nitrogen removal processes in biofilters with simultaneous nitritation and anammox

This study developed a simple numerical model for nitrogen removal in biofilters, which was designed to enhance simultaneous nitritation and anaerobic ammonium oxidation (anammox). It is the first attempt to simulate anammox together with two-step nitrification in natural treatment systems, which may have different kinetic parameters and temperature effects from conventional bioreactors. Prediction accuracy was improved by adjusting kinetic coefficients over the startup period of the biofilters. The maximum rates of nitritation and nitrite oxidation increased linearly over time during the startup period. Simulations confirmed successful enhancement of simultaneous nitritation and anammox (SNA) in the biofilters, with anammox contributing 35% of ammonium removal. Effluent ammonium concentration was affected by influent ammonium concentration and the maximum nitritation rate, and was insensitive to the maximum nitrite oxidation rate and anammox substrate factor. Ammonium removal via SNA was likely limited by biomass of aerobic ammonia oxidizing bacteria in the biofilters. The developed model is a promising tool for studying the dynamics of nitrogen removal processes including SNA in natural treatment systems.

Parametric study of a cold plasma jet generated at atmospheric pressure

The distinct discharge characteristics of an atmospheric-pressure cold plasma jet are investigated by using the temporal evolution of optical images and the discharge/substrate current. In a tube-type helium plasma jet reactor composed of a central high-voltage capillary electrode in a quartz tube and a ring-shaped ground electrode, plasma jet exhibits three discharge types, and the particular discharge type determines the variations in the discharge/substrate current and the relevant spatial characteristics of a jet. In order to find operation criteria to minimize substrate current induced material damage, we suggest diagrams of the discharge type and maximum substrate current in terms of the control parameters.

Molecular dynamics simulation of microscopic processes in Co nanocluster impact onto Cu (0 0 1) substrate

The impact of cobalt cluster with Cu (001) surface was investigated by simulating molecular dynamics (MD). A many-body potential was used based on the tight binding-second momentum approximation (TB-SMA) model to describe the interactions among atoms. The effects of cluster size, impacting cluster energy and substrate temperature were demonstrated upon the cluster’s kinetic energy, penetration deep, index and structural parameter. Furthermore, this paper studied the maximum substrate temperature, the number of disordered atoms in substrate, cluster implantation atoms and substrate sputtering atoms. The simulation results showed that the increasing cluster size and impacting cluster energy can lead to the increasing slope of energy transformation in the impact stage. In addition, the impacting cluster energy rather than cluster size and substrate temperature mainly affected penetration and diffusion processes. At the end of the paper, it was shown that the cluster’s structural parameter was affected by the cluster size, impacting cluster energy and substrate temperature.

Karakterisasi Enzim Amilase Dari Kecambah Biji Jagung Ketan (Zea mays ceratina L.)

The research about characterization of the amylase enzyme from germination glutinous corn seed ( Zea mays ceratina L.) was done. The aims of this research is to know the effect of germination time to the activity of the amylase enzyme and characteristics of the amylase enzyme from germination glutinous corn seed ( Zea mays ceratina L.). The research was conducted through four phases that is germination stage, extraction, isolation, and characterization. The research device used was Completelly Randomized Design (CRD) and to be continued by BNJ test critical level 5%. Result showed that the germination time that produces the highest activity was 36 hours and the activity of enzyme was 0.0557 sec -1 . Isolation of the amylase enzyme purified by salting out method used technical (NH 4 ) 2 SO 4 at concentration 55% with activity of 0.0394 sec -1 . The optimum pH was 9, and the activity of enzyme was 0.0207 sec -1 . Maximum substrate concentration with the activity 0.0476 sec -1 give at 12.5% (w/v), while the optimum temperature for activity 0.0229 sec -1 was 70 o C. From examination manner analysis for all of free variables results very real effect on the amylase enzyme activity, while the BNJ test critical level of 5% showed a real difference with the other treatments of every variable.

Effect of Ascophyllum extract application on plant growth, fruit yield and soil microbial communities of strawberry

Alam, M. Z., Braun, G., Norrie, J. and Hodges, D. M. 2013. Effect of Ascophyllum extract application on plant growth, fruit yield and soil microbial communities of strawberry. Can. J. Plant Sci. 93: 23–36. Plant growth and associated soil microbials were examined in several strawberry cultivars following treatment with extracts from the marine algae Ascophyllum nodosum [soluble Ascophyllum extract powder (SAEP)]. Greenhouse and field experiments were established over plots of Albion, Camarosa, Chandler, and Festival strawberries from 2009 to 2011. Soluble Ascophyllum extract powder was applied once or twice per week, or once per 2 wk at rates of 0 (control), 1, 2 or 4 g L−l over approximately 8 wk. Subsequent rooting studies examined weekly applications of SAEP at 0, 0.2, 0.4, 1 or 2 g L−1. Results indicate that maximum plant and berry productivities were found at 1 and 2 g SAEP L−1 in both field and greenhouse. Chandler was the cultivar most responsive to SAEP application, while Albion was the least responsive. Soluble Ascophyllum extract powder increased colony counts in greenhouse and field soil samples with maximum colony counts at 4 g L−1 SAEP in the greenhouse, and 1 and 2 g L−1 SAEP in the field. Metabolic activities of soil microbes were found to increase following SAEP applications. Using the Biolog microbial analysis system, maximum average well colour development (AWCD), substrate diversity (H), substrate evenness (E), and substrate richness (S) responses were found at 4 g L−1 SAEP in the greenhouse. However, in field trials, AWCD, H, E, and S responses to extract treatment showed successive increases at 1 and 2 g L−1 SAEP, but reduced effect at 4 g L−1. Soluble Ascophyllum extract powder treatment showed highest respiration rates between 0.10 and 0.40 g per week per plant while in vitro soil treatments with 4 g L−1 SAEP reduced microbial respiration. This study suggests that SAEP applications increased strawberry root and shoot growth, berry yield and rhizosphere microbial diversity and physiological activity.

Characterization of an Isoeugenol Monooxygenase (Iem) from <i>Pseudomonas nitroreducens</i> Jin1 That Transforms Isoeugenol to Vanillin

The isoeugenol monooxygenase (iem) gene from Pseudomonas nitroreducens Jin1, responsible for the conversion of isoeugenol to vanillin, was cloned and overexpressed in Escherichia coli. The purified Iem had a predicted molecular mass of 54 kDa. The V(max), K(M), and k(cat) values for it, using isoeugenol as substrate, were 4.2 µmol vanillin min(-1) mg(-1) of protein, 120 µM, and 3.8 s(-1), respectively. Maximum substrate turnover for Iem occurred at 30 °C and pH 9.0. An (18)Oxygen-labeling experiment revealed that oxidative cleavage of isoeugenol by Iem was catalyzed via a monooxygenation reaction, and that incorporation of the oxygen atom from O(2) into vanillin was preferable to incorporation from water. While the catalytic activity of Iem, as prepared, did not require the addition of any organic or metal cofactor, ICP-MS analysis showed 0.7 mol of iron per mol of Iem. Moreover site-directed mutagenesis of Iem of four conserved histidine residues individually, His(167), His(218), His(282), and His(471), which appear to be involved in ligand bonding with Fe(2+), resulted in a loss of activity. Enzyme activity was not appreciably influenced by preincubation of Iem with high concentrations of chelators, suggesting that iron is tightly bound. Iem has an iron-mediated mechanism that is widely spread among the three domains of life.

Low-Temperature (10°C) Anaerobic Digestion of Dilute Dairy Wastewater in an EGSB Bioreactor: Microbial Community Structure, Population Dynamics, and Kinetics of Methanogenic Populations

The feasibility of anaerobic digestion of dairy wastewater at 10°C was investigated in a high height : diameter ratio EGSB reactor. Stable performance was observed at an applied organic loading rate (OLR) of 0.5–2 kg COD m−3 d−1 with chemical oxygen demand (COD) removal efficiencies above 85%. When applied OLR increased to values above 2 kg COD m−3 d−1, biotreatment efficiency deteriorated, with methanogenesis being the rate-limiting step. The bioreactor recovered quickly (3 days) after reduction of the OLR. qPCR results showed a reduction in the abundance of hydrogenotrophic methanogenic Methanomicrobiales and Methanobacteriales throughout the steady state period followed by a sharp increase in their numbers (111-fold) after the load shock. Specific methanogenic activity and maximum substrate utilising rate (A max) of the biomass at the end of trial indicated increased activity and preference towards hydrogenotrophic methanogenesis, which correlated well with the increased abundance of hydrogenotrophic methanogens. Acetoclastic Methanosaeta spp. remained at stable levels throughout the trial. However, increased apparent half-saturation constant (K m) at the end of the trial indicated a decrease in the specific substrate affinity for acetate of the sludge, suggesting that Methanosaeta spp., which have high substrate affinity, started to be outcompeted in the reactor.

Biological treatment of dairy wastewater using activated sludge

The objective of the research was to evaluate the performance of a laboratory-scale biological treatment unit for dairy-industry wastewater and to determine the kinetic parameters for the activated sludge process. A laboratory-scale treatment unit comprising an aeration tank and final clarifier was used for this purpose. The treatment unit was operated continuously for three months by varying the hydraulic retention times from 2 to 12 days. The biological oxygen demand (BOD) of the influent and effluent and the mixed liquor suspended solids of the aeration tank were determined at various detention times to generate data for the kinetic coefficients. The kinetic coefficientsk (maximum substrate utilization rate), Ks (half velocity constant), Y (cell yield coefficient), and Kd (decay coefficient) were found to be 4.46 day 1 , 534 mg/l, 0.714, and 0.038 day 1 , respectively, based on the BOD. These coefficients may be used for the design of activated sludge

Bioremediation of Phenanthrene by Mycoplana sp. MVMB2 Isolated from Contaminated Soil

AbstractThe effect of nutrient and surfactant addition on the biodegradation of phenanthrene was studied in a batch scale soil–slurry system using isolated Mycoplana sp. MVMB2strain. The study was conducted using an artificially phenanthrene spiked and as well as contaminated soil from petrochemical industrial site. Maximum phenanthrene degradation and subsequent high microbial growth were observed at optimum pH (pH 6) and C/N/P ratio (100:20:3). To investigate maximum substrate degradation potential of Mycoplana sp. MVMB2, very high concentrations of phenanthrene (50–200 mg/kg soil) were used. The organism was capable of degrading >60% for a concentration below 20 mg/kg soil and >40% for concentrations up to 200 mg/kg within 8 days. Further the influence of five different surfactants namely Span 80, Tween 20, Triton X‐100, cetyl trimethyl ammonium bromide, and sodium dodecyl sulfate were tested at their critical micelle concentration (CMC) levels for phenanthrene degradation in the soil. The addition of surfactant enhanced the biodegradation and a maximum of 84.49% was obtained for Triton X‐100. Complete phenanthrene degradation by Mycoplana sp. MVMB2 was observed at 3 CMC concentration of Triton X‐100. The optimized parameters obtained were used for the degradation of phenanthrene present in the contaminated soil and 98.6% biodegradation was obtained. Thus, the results obtained in the study suggested that biodegradation of phenanthrene by Mycoplana sp. MVMB2 appeared to be feasible to remediate phenanthrene rich contaminated sites.

Degradation of High-Frequency Noise in nMOSFETs Under Different Modes of Hot-Carrier Stress

In this paper, high-frequency noise under different hot-carrier (HC) stress modes in nMOSFETs has been characterized and analyzed. The experimental results revealed a significant larger increase in NF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Rn</i> under maximum substrate current <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IB</i> , max stress or hot hole injection <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">inj</sub> than hot electron injection <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">inj</sub> . It is suggested that the difference in high-frequency noise after stress strongly depends on the type of defects generated during HC stresses. Our results provide experimental verification that the shallow interface states/traps at the Si/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface introduced by HC stress play an important role in the degradation of high-frequency channel noise.

Influence of impact angle on the interaction between Co55 nanocluster and Cu (0 0 1) substrate: Ionized cluster beam deposition

Using a classical molecular dynamics method, the influence of impact angle was studied on the ionized cluster beam (ICB) deposition. A many-body tight binding potential was employed to simulate the interactions among the atoms, in which the Co55 (55atoms/cluster) nanocluster with the total energy of 110eV was deposited on a Cu (001) substrate, whose temperature was set at 300k. The quantitative of kinetic energy of the cluster, maximum temperature substrate, cluster center of mass and diffusion area of the cluster were proposed to evaluate the interacting mechanism nanocluster and substrate. Also, the influence of impact angle was investigated on the Co–Co and Cu–Co radial distribution function and the adhesion between cluster and substrate. The simulation data demonstrated the decrease of the maximum temperature substrate with the increase of impact angle. The results indicated the decrease in the maximum depth penetration with the increase in the impact angle. The thin film formed by Co55 nanocluster with the impact angle of 30° had the minimum adhesion with the substrate.

A New Sensing Metric to Reduce Data Fluctuations in a Nanogap-Embedded Field-Effect Transistor Biosensor

A new sensing metric is proposed for a field-effect transistor (FET)-based biosensor. As proof of concept, a nanogap-embedded FET is studied to reduce data fluctuations that originate from process variations during FET fabrication and environmental variations stemming from bioexperiments. The new sensing metric utilizes a crucial gate voltage ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> @ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sub,max</sub> ), which induces the maximum substrate current. The new sensing metric shows higher immunity against variations of the nanogap length, compared with the commonly used metric that relies on threshold voltage or drain current. The proposed metric also shows smaller fluctuation, which is caused by environmental variation coming from biotreatment steps. This analysis is verified experimentally and proved by device simulations. For simple analysis, the effect of external charge of the biomolecules is eliminated by using peptide nucleic acid, which is an electrically neutral biomolecule. Thus, by using such biomolecules, the permittivity effect rising from the biomolecules within the nanogap of the gate dielectric is investigated.